Retinitis Pigmentosa (RP) is a degenerative retinal disease characterized by eventual loss of photoreceptor cells. Extensive evidence from studies of normal animals and dystrophic animal models indicates that the PE plays an important role in maintaining visual cell function. Visual failure in RP may be secondary to dysfunction of the retina and pigment epthelial cells (PE). Studies on RP would be greatly facilitated having a culture model system of PE cells with which to study both normal and pathological states. However, culturing PE cells is exceedingly difficult, differentiated epithelial cells maintained under the usual culture conditions undergo rapid morphological and biochemical deterioration resulting in a loss of the differentiated state. Studies by others have overcome this impasse. New culture conditions include more sophisticated basal media, serum-free media with supplements of hormones designed for each cell type, and substrata of appropriate forms of extracellular matrix. We propose to develop a culture model system of PE cells utilizing these new principles elucidating conditions for maintenance of differentiated epithelial cells. PE cells will be obtained from fetal and adult eyes and cultured on various forms of extracellular matrix: biomatrix from mammalian eyes, basement membrane derived from human amniotic membranes, rat tail collagen (type 1), and basement membrane collagen (type IV). We hope that one of the substrata mentioned above will give us cultures of PE cells with better long-term survival and functioning approximating the morphological and biochemical parameters found in vivo. If one enables the cultures of PE cells to survive longer, we will then search for optimal basal media (e.g. Ham's F12 or his new media for keratinocytes) and thereafter work on developing a serum-free, hormonally defined medium. The cultures will be characterized for a number of parameters indicative of PE cell functioning in vitro, viz: retention of epitheloid morphology; polarity; capacity to form apical villi, occluding junctions; capacity for phagocytosis of rod outer segments. Our ultimate goal is to study receptor mediated phagocytosis in these cells by using electromicroscopic and immunological techniques. The development of conditions permitting culture of PE cells should also permit culturing of cells from RP patients,, and to make comparisons of the normal versus abberant (RP) physiology and phagocytosis in human PE.